JP2003320457A - Method for mig welding titanium and titanium alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for MIG welding titanium or a titanium alloy which can stably and efficiently weld at a job site by a semi-automatic welding by using the method for MIG welding the titanium or the titanium alloy and which can reduce a cost by decreasing a shielding gas using quantity by shortening a welding time. <P>SOLUTION: The method for MIG welding the titanium or the titanium alloy comprises a step of welding by using a welding wire of a pure titanium or titanium alloy having a surface roughness: 1.0 to 5.0 μm and a maximum roughness (Rmax) of 10 μm or less in the MIG welding of the titanium or the titanium alloy, and using a pulse welding current which satisfies the conditions that the MIG welding satisfies 300 A≤(peak current)≤500 A, 2.0≤(peak current)/(base current)≤5.0. Thus, the MIG welding is conducted stably without bringing about a wandering phenomenon. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium alloy welding wire for MIG welding, which is used for welding titanium or titanium alloy members used in ships, building structures and the like.

[0002]

2. Description of the Related Art Conventionally, titanium or titanium alloy has been
It is used in ships, building structures, automobiles, motorcycles, etc., which require high corrosion resistance, and the amount of its use has been increasing more and more recently. At the time of welding this titanium or titanium alloy, the TIG welding method (tungsten inert gas metal welding method), which is one of the non-consumable electrode welding methods, is mainly used at present. On the other hand, the MIG welding method (inert gas metal arc welding method), which is a consumable electrode type welding method, has an advantage that welding efficiency is several times or more higher than that of the TIG welding method. When MIG welding is performed using a welding wire, the welding arc becomes extremely unstable.

This is the MIG of titanium and titanium alloys.
When welding is performed by the welding method, since the arc maintains the cathode spot, the arc moves violently to the position where the surface oxide film of the material to be welded of titanium and titanium alloy remains and the wandering phenomenon occurs and the welding spatter occurs. Occurs in a large amount, and spatter adheres to titanium and titanium alloy as a base material. Further, there is a problem that the welding bead meanders due to this wandering phenomenon, and the appearance of the welded portion frequently occurs. Therefore, titanium and titanium alloys are
The danger of welding with the G welding method has been avoided as much as possible.

On the other hand, when the TIG welding method is adopted, an arc is generated using a non-consumable electrode having a high melting point, and welding is performed while supplying a welding wire to the molten pool generated in the base material. Therefore, no spatter is generated. Further, since the electrode side has a negative polarity and the welded side has a positive polarity, the wandering phenomenon does not occur due to the cleaning action of removing the oxide film generated on the surface of the material to be welded. The bead does not meander and a good weld appearance shape is obtained. For this reason, the TIG welding method has been exclusively used for welding titanium and titanium alloys.

Further, in TIG welding, it is necessary to hold the welding torch in an appropriate position and also hold the welding wire in an appropriate position. Therefore, although it is good when it is possible to prepare a device that can hold the welding torch and the welding wire in an appropriate position in a factory or the like, when the non-welded object is a large structure,
The welding operator must hold the welding torch, the welding wire, and the like at appropriate positions and move as the welding progresses, so the burden on the welding operator cannot be imagined. Further, the one in which the guide device for feeding the welding wire is incorporated in the welding torch is extremely expensive as compared with the semi-automatic welding torch for MIG welding. In addition, TIG
The welding has a problem that the welding heat input is smaller than that of the MIG welding and thus the welding time is long, resulting in poor welding efficiency. In addition, since the welding time is long, the amount of gas used as the shielding gas is large and the cost is high.

For example, in Japanese Patent Publication No. 59-226159, two end faces in the lengthwise direction of two titanium strips having a worked structure are butted against each other and TIG-welded to soft-anneal a base metal portion in the vicinity of the welded portion. A method of connecting titanium strips without breaking is disclosed. As described above, conventionally, when the titanium strip is welded, the welding is mainly performed by the TIG welding method. Further, in Japanese Patent Publication No. 12-280076, a shield gas in which a trace amount of an oxidizing gas is added to an inert gas and a consumable electrode of titanium or a titanium alloy are used to conduct a pulse welding current for welding titanium or A method of arc welding a titanium alloy is disclosed. However, supplying oxygen or oxides from the shielding gas not only stabilizes the welding arc, but also a large amount of oxygen is mixed in the weld metal, which hardens the weld and reduces the elongation. Will be deteriorated.

[0007]

In view of the above-mentioned problems of the prior art, the present invention uses titanium or titanium alloy for MIG.
Titanium alloy welding wire for MIG welding, welding method and welding that enables stable and highly efficient on-site welding by semi-automatic welding by using the welding method and achieves cost reduction by reducing shield gas usage by shortening welding time It provides metal.

[0008]

The present invention has been made to solve the above-mentioned problems, and its gist is to provide a surface roughness of 1.0 in MIG welding of titanium or a titanium alloy.
Has a maximum roughness (Rmax) of 10
A MIG welding method of titanium and a titanium alloy, which uses pure titanium or a titanium alloy welding wire of μm or less, and preferably uses a pulse welding current satisfying the following conditions.

300A ≦ (peak current) ≦ 500A 2.0 ≦ (peak current) / (base current) ≦ 5.0

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION First, a welding apparatus used for MIG welding will be described with reference to FIG. In FIG. 1, a welding wire 3 is provided in the center of a material to be welded 1 directly above a welding site, and a shield gas 4 supplied from a shield gas supply device 3 separately provided on the outer periphery of the welding wire 3 is injected toward a molten base 5. A torch 2 for MIG welding having an injection port is arranged, and a welding current is passed to perform a welding operation to form a welding bead 6. In general, titanium or a titanium alloy is more likely to be oxidized at a lower temperature than steel or the like, and in a gas shield having only a tip of a welding torch used for steel, the weld metal is oxidized and hardened, and good elongation of the weld metal cannot be obtained. Therefore, a shield box is provided behind the welding torch immediately after welding, and the area behind the welding arc point is also shielded with an inert gas such as Ar gas.

The shield gas supply device 3 used in the present invention temporarily takes in the shield gas supplied from the shield gas supply pipe 3-1 into the shield box 3-2, and the shield gas is supplied into the shield box 3-2. So as to be uniformly supplied to the surface of the welding bead 6, the gas supply pipe 3-3 is arranged parallel to the welding direction, and the gas outlet 3
-4 is provided at the outlet opposite to the welding bead 6 and a shielding gas 4'which is injected from the gas outlet is applied to the upper wall in the shield box 3-2, and then applied to the welding bead 6 on the lower surface. It

FIG. 2 shows the spatter scattering state due to the wandering phenomenon when MIG welding is performed by the conventional method.
Further, FIG. 3 shows a schematic view of the appearance of the weld beads.
As shown in FIG. 2, M of conventional titanium and titanium alloy
In IG welding, the welding arc becomes extremely unstable because the arc maintains the cathode spot, and the welding spatter occurs due to the wandering phenomenon where the arc moves violently to the position where the surface oxide film of the workpiece is left and violates. Is generated, and the spatter 7 scatters and adheres to the surface of the base material. Further, as shown in FIG. 3, in addition to the above-mentioned spattering and adhesion of spatter, the welding bead meanders due to the wandering phenomenon, resulting in poor appearance of the welded portion and reduced strength of the weld metal. In FIG. 3, when the wandering phenomenon occurs, a trace of the arc moving in the waviness width direction due to the wandering phenomenon remains on the outside of the weld bead start end portion, resulting in an extremely poor weld bead shape.

Therefore, in the present invention, in the MIG welding of titanium or titanium alloy, the surface roughness: 1.0 to
Has 5.0 μm and maximum roughness (Rmax) of 10 μ
Using pure titanium or titanium alloy welding wire of m or less,
Further, by using a pulse welding power source, preferably by using a pulse welding current satisfying the following conditions, a wandering phenomenon is not caused and stable MIG welding is found.

300A ≦ (peak current) ≦ 500A 2.0 ≦ (peak current) / (base current) ≦ 5.0 Generally, if a small amount of oxygen is added to the shield gas or welding wire, the welding arc is likely to be stable. It has been known. Conventionally, oxygen is added to this shielding gas and chemical components during welding wire production. However, such addition of oxygen to the shielding gas or the welding wire causes high cost. MI of titanium and titanium alloys
In the G welding method, it is required to stabilize the welding arc and reduce spatter. Therefore, the present inventors
As a result of diligent research into means for effectively supplying oxygen into the welding arc, the surface roughness of the welding wire is roughened and the surface area of this wire is increased to make it easier for the welding wire to react with oxygen in the air. It was found that titanium oxide was formed on the surface of the welding wire. This has made it possible to add a small amount of oxygen to the welding arc.

For this purpose, the surface roughness of the welding wire is 1.0 to 5.0 μm, and the maximum roughness (Rmax) is 10 μm.
It must be m or less. The surface roughness is 1.0 to 5.
If it is in the range of 0 μm, the welding arc is stabilized,
At the same time, there are few wandering phenomena, the width of the wandering phenomenon is about 0 mm, and the meandering of the welding bead is also reduced.
A good bead appearance is obtained. On the other hand, when the surface roughness is 1.0 μm or less, or 5.0 μm or more, the welding arc becomes unstable and the wandering phenomenon becomes large, but the arc does not move beyond the welding bead width. Therefore, the width of the wandering phenomenon becomes approximately 0 mm, but since the wandering phenomenon is large, the meandering width of the welding bead is large and good welding cannot be performed.

Next, the maximum roughness (Rmax) of the welding wire
Is set to 10 μm or less because the maximum roughness becomes large,
The friction generated between the inside of the conduit cable, through which the welding wire passes between the wire feeder and the welding torch, and the surface of the welding wire increases, which causes the welding wire's feeding resistance and buckling of the welding wire. It causes unevenness of wire feeding. In particular, uneven feeding of the wire is a factor that hinders the stability of the welding arc and increases the wandering phenomenon and the generation of spatter. If the maximum roughness (Rmax) exceeds 10 μm, wire feeding unevenness occurs, the arc becomes unstable, the wandering phenomenon becomes large, and the welding bead meandering width becomes large and good welding is achieved. I think I can no longer. On the other hand, when the maximum roughness is 10 μm or less, uneven feeding of the wire does not occur, and the instability of the arc due to the uneven feeding does not occur. It is considered that the meandering width changes.

Further, in the present invention, in MIG welding, a pulse welding power source is used as a welding power source, and the welding power source is 300A.
Welding with a pulse welding current satisfying the conditions of ≤ (peak current) ≤ 500 A and 2.0 ≤ (peak current) / (base current) ≤ 5.0 does not cause a wandering phenomenon and is stable. It is preferable to adopt the conditions under which MIG welding can be performed. That is, as shown in FIG. 5, extremely good weld beads (⊚ in FIG. 5) can be obtained by MIG welding under the above conditions. Even if the above conditions are not satisfied, a good weld bead (◯ in FIG. 5) can be obtained. The above good weld bead appearance means a wandering phenomenon width (Ww) of 0 mm and a bead meandering width (Wb) of more than 0.2 and 0.6 mm or less, and a very good weld bead appearance is a wandering phenomenon. Width (Ww)
Is 0 mm, and the meandering width (Wb) of the bead is 0.2 mm or less.

The diameter of the pure titanium or titanium alloy welding wire used in the present invention is 1.6 to 2.0 in cross-sectional outer diameter.
mm is preferred.

When titanium or titanium alloy is MIG-welded using such welding wire and adopting the welding conditions specified above, the composition of the welded part of titanium or titanium alloy is Al in mass% and is Al. : 0.5-10%, O:
A weld metal having 0 to 1.0% and the balance titanium can be obtained.

Further, in the present invention, in order to perform droplet transfer during welding regularly and smoothly, it is generally known that pulse welding current is used to control welding current in a pulsed manner for welding. However, in the MIG welding of the present invention, instead of the normal DC welding power source, the pulse welding current is used by using the DC pulse welding power source to further cause the wandering phenomenon width or the welding bead meandering width. You can

[0021]

Example 1 A welding wire having a surface roughness of 0.5 to 8.0 μm and a maximum roughness of 10 μm or less on the surface of a pure titanium welding wire. The material to be welded has a plate thickness of 12.7 mm.
Pure titanium material with maximum groove (90 °) of welding, welding peak current: 500A, welding base current: 150A, welding voltage: 30V, welding speed: 100cm / min, flow rate: 25l
/ Min Ar gas is used as a shield gas, and the diameter is 1.6
MIG welding was performed using a mmφ welding wire. Table 1 shows the surface roughness of the welding wire, the welding state, and the results of appearance evaluation.

[0022]

[Table 1]

In Table 1, the width of the wandering phenomenon means the width in which the wandering phenomenon makes the arc unstable and the wandering phenomenon becomes large, and the trace of the wandering phenomenon remains outside the starting end of the weld bead. Good, the meander width of the weld bead is a straight line parallel to the welding direction through the position where the weld bead start end is most recessed, and a straight line parallel to the weld direction through the position where the weld bead start end is most protruding. Is the shortest distance. (See FIG. 1) As can be seen from Table 1, when the welding wire surface roughness and the maximum roughness are within the conditions of the present invention, the wandering phenomenon width and the bead meandering width are remarkably reduced, and the good appearance shape is obtained. It can be seen that the weld bead of is obtained.

[0024]

As described above, the present invention enables stable or highly efficient on-site welding by semi-automatic welding of titanium or titanium alloy using the MIG welding method, and shield gas by shortening the welding time. (EN) It is possible to provide a titanium alloy welding wire for MIG welding, a welding method, and a weld metal, which reduce cost by reducing the amount used.

[Brief description of drawings]

FIG. 1 is a schematic external view of a MIG welding device.

FIG. 2 is a schematic view of the appearance of the MIG welding method.

FIG. 3 is a schematic plan view of a welding bead formed by conventional MIG welding.

FIG. 4 is a schematic plan view of a welding bead by MIG welding according to the present invention.

FIG. 5 is a diagram showing an appropriate welding current range during pulse welding.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Taiji Hase             7-6-1 Higashi Narashino, Narashino City, Chiba Prefecture             Welding Industry Co., Ltd.             Within the corporation F-term (reference) 4E001 BB08 CB04 DE04 EA01 EA10

Claims (2)

[Claims] 1. In MIG welding of titanium or titanium alloy, a welding wire of pure titanium or titanium alloy having a surface roughness of 1.0 to 5.0 μm and a maximum roughness (Rmax) of 10 μm or less is used. MIG welding method for titanium and titanium alloys, characterized in that the welding is performed by means of welding. 2. The MIG welding method for titanium and titanium alloys according to claim 2, wherein the MIG welding is performed using a pulse welding current satisfying the following conditions. 300A ≦ (peak current) ≦ 500A 2.0 ≦ (peak current) / (base current) ≦ 5.0